Toyota 1MZ-FE Engine Problems

The Toyota 1MZ-FE is a lightweight aluminum cylinder block V6 engine applied to a variety of different models for both Toyota and Lexus. The engine was first introduced to the American market in 1993, and later versions were eventually discontinued in 2014. This V6 has dual overhead cams, and the first generation came stock with 194-201 horsepower and 183-209 lb-ft of torque.

The 1MZ-FE is known for its great reliability and long engine lifespan, with many drivers expecting at least 200,000 miles without major issues. However, like any engine, the higher the mileage, the more oil consumption. Aside from oil consumption issues, a variety of other different problems may arise within the Toyota 1MZ-FE throughout time. We love the dependability of this engine, yet throughout this article, we will examine and discuss the most common problems.

Toyota 1MZ-FE Engine Problems & Reliability

What Cars Use the 1MZ-FE?

The 1MZ-FE can be found (in the American market) within the following Toyota and Lexus models listed below.


  • Camry
  • Sienna
  • Solara
  • Avalon
  • Highlander


  • RX300
  • ES300

Toyota offered a bolt-on TRD supercharger kit first in 1997 (through 2000) for the Camry, Sienna, and Solara. This kit provided an improvement, bumping the engine to 242 hp and 242 lb-ft of torque. The VVT-i system was used within the Camry, Avalon, and Sienna with 210 hp and 222 lb-ft of torque. However, future models would use a drive-by-wire/electronic throttle control. Toyota would continue to use the 1MZ-FE until introducing the 2MZ-FE and 3MZ-FE versions before discontinuation in 2014.

4 Common 1MZ-FE Engine Problems:

  • Oil consumption issues (prone to engine sludge)
  • Unreliable knock sensor
  • Issues with VVT-i
  • Potential GRE Failure

Throughout this article, we will examine and discuss the issues listed above. It’s important to note that although these issues may happen to many drivers, the 1MZ-FE has what some consider to be a bulletproof engine compared to the reliability of others. These issues may never occur for some, or be a reoccurrence for others. However, oil consumption issues are likely to occur, especially as the engine ages. In our summary, we will emphasize the durability of the 1MZ-FE and cycle back to these issues mentioned.

Regardless of the 1MZ-FE’s impressive durability, it still has an aluminum cylinder block. If this is damaged, it can require a new engine block replacement or an entire engine replacement. Luckily, this does not seem to be a common enough occurrence to make our list above. For now, let’s analyze the problems listed above with the further details discussed below.

1) Toyota 1MZ-FE Engine Oil Consumption Issues

Oil leaks can be a prevalent issue in many different makes and models. Unfortunately, one of the downfalls of the Toyota 1MZ-FE is that they are prone to oil leaks and engine sludge buildup. This can be a cause for concern as oil leaks can cause damage to an engine over time. Therefore, it’s essential to run high-quality synthetic oil on the 1MZ-FE to extend the engine’s lifespan significantly. Like most cars, proper maintenance is essential.

Sludge buildup is one of the most frequent symptoms of the 1MZ-FE’s excessive oil consumption. Fortunately, this is one of the easier symptoms to identify, especially once the front valve cover is removed. A fouled spark plug (likely spark plug #2) also hints that your engine is having oil consumption problems. Spark plug replacement costs can range upwards of $250 depending on where the part is sourced and varying labor costs. Another easily spotted problem is too much smoke exiting the exhaust, specifically as the car is started. Drivers report a blue/greyish smoke, most commonly with these sparkplug issues. Our last easily identifiable symptom of oil consumption issues is oil drippings or puddles gathering underneath the car itself.

Yet, some symptoms are not so easy to identify. For example, problems with camshaft caps (specifically on the #2 cylinder) can be an indirect sign that your 1MZ-FE has issues with oil consumption/leaks. It’s important to note that although excessive oil consumption is not generally associated with catastrophic engine failure, it can still cause significant damage to your engine. Problems ranging from valve stem leaks up to a fouled catalytic converter are all products of excessive oil consumption in the 1MZ-FE.

Oil Consumption Symptoms:

  • Sludge buildup
  • Fouled spark plug (specifically on #2 cylinder)
  • Smoke from exhaust
  • Bank #2 camshaft cap issues
  • Oil dripping/oil puddles underneath the car

2) Unreliable Knock Sensor

Regardless of the overall reliability of the Toyota 1MZ-FE, a bad knock sensor can be a common occurrence. The knock sensor detects if the vibrations coming from the engine are unusual or not. This sensor will decrease acceleration and overall power if failing. Unfortunately, the knock sensor cannot be repaired once it fails and must be completely replaced. Toyota corrected this issue by replacing the knock sensor altogether in the 3MZ-FE with a new, more durable flat-type knock sensor.

The 1MZ-FE will lose power and acceleration that should be noticeable to drivers. With the loss of power also comes a loss of efficiency. This loss of efficiency is identified by higher fuel consumption. It’s important to note that a bad knock sensor can result in an engine running too hot. A hot engine can produce an increase in emissions that can potentially fail your engine when trying to pass a state inspection test.

A bad knock sensor can be more difficult to identify compared to oil leaks or excessive oil consumption. Fortunately, the 1MZ-FE is likely to throw a code that allows for a diagnostic test that can quickly determine the source of an engine problem. An unreliable knock sensor may not cause severe damage to the engine itself. However, it can cover up extremely severe issues causing abnormal vibrations emitting from the engine. The 1MZ-FE and 2MZ-FE both have the original knock sensor from Toyota that created the most problems for drivers until Toyota replaced the sensor in the 3MZ-FE.

Bad Knock Sensor Symptoms:

  • Poor acceleration/Loss of power
  • Less MPG/Loss of fuel mileage
  • Different engine feeling at higher speeds or when carrying more weight3)

3) Toyota 1MZ-FE EGR Failure

The EGR valve is responsible for recirculating gas emissions back into the combustion chamber. This process results in a reduction of emission temperature, which then inhibits the production of NOx emissions. The EGR valve helps maintain proper fuel consumption (as well as engine emissions.) If the EGR fails, then a range of varying issues can pop up for your Toyota 1MZ-FE engine.

If you experience a rough engine idle or the engine stalling while idling, it’s essential to check the EGR valve. However, this symptom can be found commonly on our list of problems making it more challenging to find the source of the issue. A loss of fuel mileage and an increase in engine emission can also be direct results of a bad EGR valve. This problem can result in a heavy fuel smell both inside and outside of the car.

Let’s hope our previous issue is not co-occurring with EGR failure due to the fact that a failing EGR can produce knocking or cranking noises from the Toyota 1MZ-FE. This problem can be harder to diagnose than other issues listed above if not utilizing proper diagnostic equipment/tests. An EGR valve replacement for a Camry can cost up to $350 based on national averages. (Once again, this depends on the source of the replacement valve and varying labor costs)

EGR Failure Symptoms:

  • Rough engine idle/Stalling while idling
  • Increase in fuel consumption
  • Increased engine emissions
  • Heavy fuel smell
  • Knocking noises coming from the engine bay

4)Toyota 1MZ-FE Engine’s VVT-i Component Issues

VVT-i stands for variable valve technology intelligence. This system helps boost overall engine performance, improve fuel economy, and maintain proper emissions. Toyota only used this technology in the 1MZ-FE for the Avalon, Highlander, Sienna, and Camry models. The VVT-i system can create noticeable problems for these models if certain components are faulty or fail completely.

Problems with any VVT-i components can result in a rough engine idle (once again). Luckily, this problem will most likely produce a lit check engine light, making it easier to diagnose with proper testing. Another problem with the VVT-i system is the inability to accelerate correctly or maintain speed. This issue is most noticeable when accelerating and maintaining speed uphill. The repair can be one of the more costly repairs for the Toyota 1MZ-FE, with average costs ranging up to $800 plus dollars.

Symptoms of VVT-i Component Issues:

  • Rough engine idle/shaking
  • Check engine light
  • Inability to properly accelerate or maintain speed uphill

You can also check our latest post on Toyota 5VZ-FE 3.4 V6 Engine Problems.

Toyota 1MZ-FE Engine Problems Summary

The Toyota 1MZ-FE is well known for its exemplary reliability and durability. Most drivers will be disappointed if their 1MZ-FE does not reach 200,000 miles without major issues. However, engine longevity is based upon many variables such as proper maintenance, proper repairs, and specifically the usage of high-quality synthetic oil. The aluminum engine block will need to be entirely replaced if broke, or even a new engine altogether. Fortunately, we don’t find that issue to be a common occurrence for most 1MZ-FE engines.

Yet, as we discussed, oil leaks seem to be a prevalent issue for most models that use the 1MZ-FE. These can result in engine sludge buildup, leading to engine deterioration, less overall power and performance, loss of fuel efficiency, and increased emissions. So again, be sure to use high-quality oil and practice proper maintenance to extend the lifespan of this engine.
The knock sensor was replaced in the 3MZ-FE, correcting the issue some drivers experienced. VVT-i issues are obviously only applicable to the specific models that use that system. It’s still important to make sure your VVT-i components are functioning properly.

EGR failure can cost up to $350 on average, depending on where parts are sourced and differentiating labor costs. Lots of these issues are a product of poor maintenance. Therefore, the Toyota 1MZ-FE can be an extremely dependable daily driver, but only with proper care.

Most drivers should expect their 1MZ-FE to easily last up to 200,000 miles without any major repairs needed. Let us know in the comments below your experience with the 1MZ-FE engine’s reliability and durability!

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One Comment

  1. I have a 2001 Toyota Sienna with 1MZ-FE engine I am the original owner and it has 448,000 with the original engine and transmission. I have been using Castrol Full Synthetic oil as well as their Full Synthetic Transmission fluid. In the beginning I would change the oil and filter (Toyota) every five thousand miles. Once I hit four hundred thousand miles I started changing the oil at three thousand miles. I monitor the oil quality at the dip stick every fill up. I always felt it important to use OEM oil filters and air filters to protect the engine. Finally I change the PCV valve regularly and monitor the coolant temperature with an added OBD heads up display on the dash.

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